1. Field of the Invention
Apparatuses consistent with the present invention relate to a lighting device which divides light into a plurality of monochromatic light beams, such that each beam corresponds to a pixel and a display device which employs the lighting device and has improved light usage efficiency.
2. Description of the Related Art
Flat panel displays are classified as emissive displays, which form images by emitting light themselves, or as non-emissive displays, which form images by receiving light from an external source. For example, a non-emissive flat panel display device such as a liquid crystal display (LCD) requires an additional light source such as a backlight unit.
Since non-emissive flat panel display devices cannot use all the light emitted by the light source efficiently, they have low light usage efficiency.
For example, LCDs are manufactured by injecting liquid crystal material between substrates on which electrodes are disposed. Liquid crystal molecules of the liquid crystal material are moved by an electric field generated by applying a voltage between two electrodes, and thus, an image can be displayed by altering the transmissivity of light according to a state of the liquid crystal molecule. The liquid crystal layer within an LCD acts as a shutter to block or transmit polarized light, as the polarization properties of the liquid crystal layer are altered based on the voltage applied between the electrodes. Polarization plates are formed on both surfaces of the LCD. Since the polarization plates formed on both surfaces of the LCD transmit light polarized in one direction and absorbs light polarized in other directions, they are absorbing polarization plates. The absorbing polarization plates absorb about 50% of the emissive light, and therefore, an LCD employing the same has a low light efficiency.
In order to realize a color image, an LCD includes Red (R), Green (G) and Blue (B) color filters. The color filters are formed using dyes and pigments. Each color filter only transmits light corresponding to a color having a corresponding wavelength. Thus, they each absorb ⅔ of the light incident thereon, which provides another source of low light efficiency.